The invention relates to electric equipment of a vehicle having an at least partially electric braking and steering device containing an electric or electro-mechanical steering device.
A combined and at least partially electric braking and steering device of a vehicle is known from the genus-forming document EP 0 999 117 A2. There is provision here that in the event of a fault in a steering system component, in particular a steering actuator, individual wheels for maintaining the steerability of the vehicle are selectively braked. As a result, the fault tolerance in the event of a failure of a steering system component is improved by virtue of the fact that an attempt is made to at least partially replace the failed steering effect of the respective steering system component by generating a yawing moment by selective braking of individual wheels. In order to increase the fail safety, the power supply of the combined braking and steering device is redundant in the form of a further vehicle battery. Furthermore, wheel modules in which braking and steering actuators are accommodated also each have a separate energy store. In this context, the electronic steering and braking controller and the energy supply are configured completely redundantly, i.e. all the electronic system components and the energy supply are each present in duplicate at least. As a result, when an electronic system component or energy supply fails, the respective still intact system component or energy supply can completely take over the requested function. A disadvantage of this system configuration is the relatively costly installation and the high component costs and system costs. As a result, such concepts are compatible with series production only to a limited degree. Furthermore, it is necessary to ensure that no faults occur simultaneously in the redundant systems. The steering and braking inputs for the electric braking and steering device are also generated by the driver.
On the other hand, for a considerable time there have been to a certain extent driver assistance systems such as traction control systems (TCS), emergency braking assistance systems (AEBS), adaptive cruise control systems (ACC) or vehicle movement dynamics control systems (ESP) which can be used to carry out steering and/or braking interventions automatically and independently of the driver, in order to ensure safety specifications such as e.g. a certain minimum distance from the vehicle traveling ahead, a certain minimum braking effect as well as a certain minimum level of driving stability.
For future vehicle traffic, concepts are also planned which permit vehicles in public road traffic also to move completely without intervention by a driver, in the manner of an “autopilot”. In this context, a plurality of vehicles are to drive under automatic control one behind the other at a distance which is smaller than an actually prescribed safety distance (platooning). This is possible only if all the vehicles can brake simultaneously and with the same deceleration by virtue of suitable communication between them.
Within the scope of such (partially) autonomous vehicle concepts it is therefore necessary for the electric braking and steering device to be able to receive and implement braking and steering requests electronically, specifically even when there is a fault within the electronic controllers or electrics. Therefore, a fault-tolerant controller of the braking and steering device is required so that when faults occur in the brake system the core functions of steering and braking can be ensured even without (intervention by) a driver, at least over a certain time, until a safe system state is reached, for example at least a stationary state of the vehicle or a parked state with permanently applied brakes.
In electronic or electronically brake-pressure-regulated brake systems (EBS) which are installed in series at the time of this patent application, the electronic control device of said brake systems switches off when a fault occurs in the electric service brake circuit (e.g. failure of the electric energy source or of the electronic control device itself) and switches over to a purely pneumatic backup controller by using the at least one pneumatic service brake circuit. However, with a pneumatic service brake circuit only the driver can brake the vehicle by activating the service brake activation element. Such a system is not suitable for (partially) autonomous or automated driving (autopilot) as described above, since, when such a fault occurs, automated controlled steering and braking interventions are no longer possible.
The German patent application with the file number DE 102014112014.0 which is not yet published and is by the same patent applicant deals with the case of a pneumatic or electropneumatic service brake device having the possibility of being activated not only by a driver's braking request but also automatically by a driver assistance system such as, for example, an emergency braking assistant or an adaptive cruise control system (ACC). In this context, use is made of a service brake valve device which is expanded compared to the prior art or expanded foot-operated brake module with at least one pneumatic channel in which a control piston can be loaded not only by a first activation force generated by activation of the foot-operated brake pedal but also additionally by a second activation force which is generated electronically as a function of driving operation conditions. In particular, the expanded service brake valve device is provided with an electronic pressure control or regulating device with which the brake pressure or brake control pressure which is generated in the at least one pneumatic channel can be increased or reduced independently of the driver by the second activation force which acts on the control piston.
In a brake system which is known from DE 10 2014 107 399 A1, the electronic brake actuation system is configured with a dual circuit or multiple circuit in such a way that each brake circuit serves only certain axles or wheels. In the event of a failure of one of the brake circuits, therefore just a portion of the possible braking effect can be generated electronically. If a brake circuit failure were to occur, for example, during strong braking of an automatically controlled vehicle column (platooning) as described above, a rear-end collision would be unavoidable.
Taking this as a basis, the object of the invention comprises developing an at least partially electric braking and steering device in such a way that when actuation occurs it has a level of fail safety which is as high possible and ensures the strongest possible braking effect without intervention by the driver, for example by using a driver assistance system or by an autopilot device.
According to the invention there is provision that an electropneumatic service brake device, in particular an electronic or electronically brake-pressure-regulated brake system (EBS), is provided as a service brake device, which contains an electropneumatic service brake valve device, an electronic brake control device, electropneumatic modulators and pneumatic wheel brake actuators. The electronic brake control device electrically controls the electropneumatic modulators in order to generate pneumatic brake pressures or brake control pressures for the pneumatic wheel brake actuators wheel-specifically, axle-specifically or side-specifically. The electropneumatic service brake valve device has a service brake activation element and, within at least one electric service brake circuit, at least one electrical channel with at least one electric brake value generator which can be activated by the service brake activation element and has the purpose of outputting activation signals as a function of activation of the service brake activation element. The electropneumatic service brake valve device also has at least one electronic evaluation device which receives the activation signals and inputs braking request signals into the electronic brake control device as a function of the activation signals. The electropneumatic service brake valve device further has within at least one pneumatic service brake circuit, at least one pneumatic channel in which, by activating the service brake activation element on the basis of a driver's braking request, at least one control piston of the service brake valve device is loaded with a first activation force. The control piston directly or indirectly controls at least one double seat valve of the service brake valve device having an inlet seat and an outlet seat, in order to generate pneumatic brake pressures or brake control pressures for the pneumatic wheel brake actuators. The electropneumatic service brake valve device also is capable of generating a second activation force independently of a driver's braking request are provided, acting on the at least one control piston in parallel with the first activation force (in the same direction as or in the opposite direction to said force) when a braking request which is independent of the driver's request is present. The electropneumatic service brake device is supplied with electrical energy by a first electrical energy source or by a first energy supply circuit, which energy source is independent of a second electrical energy source or a second energy supply circuit. The first electrical energy source or the first energy supply circuit supplies the electropneumatic service brake valve device with electrical energy, and the electric or electro-mechanical steering device is supplied with electrical energy by the second electrical energy source or by the second energy supply circuit.
Generally, a vehicle which is suitable for autonomous or automated driving requires at least one steering device which can be influenced electrically, for example in the form of steer-by-wire without a continuous mechanical connection between the steering wheel and the steering gear mechanism or in the form of a superimposition steering system in which even though there is a continuous mechanical connection between the steering wheel and the steering gear mechanism, a steering torque which is generated by an electric steering actuator is superimposed on the steering torque generated by the driver via the mechanical connection (steering torque superimposition). In electric superimposition steering systems in heavy utility vehicles, a conventional hydraulic power steering system is usually also connected downstream, which power steering system amplifies the driver's specifications and the superimposition steering systems in order thereby to be able to apply the high steering forces. The electric or electro-mechanical steering device which is used for the invention is embodied in such a way. Furthermore, there is also a need for a brake device which can be influenced electrically. An electropneumatic service brake device which is used for the invention and has an EPS function, in particular an electronic or electronically brake-pressure-regulated brake system (EBS) with an ESP function satisfies this requirement.
The basic principle of “steering by braking” is sufficiently known and is described, for example, in EP 0 999 117 A2 which has already been mentioned above. In this context use is made of the fact that a vehicle can be steered even by braking individual wheels or wheel groups. Therefore, a suitably designed service brake device can serve as a redundancy for the steering device at least for a limited time period.
A suitable service brake device constitutes an electropneumatic service brake device such as is used for the invention and which is able to input brake pressure into pneumatic wheel brake actuators in a wheel-specific or wheel-group-specific fashion without involving the driver. This involves electropneumatic service brake devices which can carry out a driving stabilization function such as ESP (electronic stability program) or ABS (anti-lock brake system) in combination with TCS (traction slip control system) valves on the front axle and rear axle.
In order to ensure “steering” and “braking” in an automated fashion, i.e. on the basis of authority other than the driver's (autopilot device) even in the case of a fault in the electrical energy supply, in a vehicle with the equipment according to the invention, at least two energy supply circuits are necessary which are configured in such a way that in the case of a fault in one of the circuits there is still sufficient electrical energy present in order to be able to continue to operate the combined steering and braking device. An autopilot device is to be understood in the following as being a device which closed-loop or open-loop controls at least the steering and braking device of the vehicle without involvement of the driver, in particular as a function of the driving operation conditions. The same also applies to a vehicle movement dynamics controller such as e.g. adaptive cruise control (ACC) by which the distance or the relative speed with respect to a vehicle traveling ahead is kept constant (emergency braking assistant (AEBS) or vehicle movement dynamics controller (ESP) with the aid of which steering and/or braking interventions can be carried out automatically and independently of the driver, in order to ensure safety specifications such as e.g. a certain minimum distance from a vehicle traveling ahead, a certain minimum braking effect as well as a certain minimum level of driving stability.
In the case of the invention, an electropneumatic service brake device, in particular with an ESP function, serves as a redundancy for the failed electric or electro-mechanical steering device. Different variants of electropneumatic service brake devices are suitable for this.
According to a first variant of the electropneumatic service brake device, the brake pressure in pneumatic wheel brake actuators of the vehicle, and, if appropriate, in pneumatic wheel brake actuators of a trailer of the vehicle, is closed-loop or open-loop controlled purely pneumatically only in the event of a fault in the electric service brake circuit and in the event of activation of the brake pedal by the driver, and otherwise is always closed-loop or open-loop controlled electrically. This is the case in an electronically brake-pressure-regulated EBS system which is always equipped with an ESP function.
According to a second variant of the electropneumatic service brake device, the brake pressure in pneumatic wheel brake actuators of the vehicle, and, if appropriate, in pneumatic wheel brake actuators of a trailer of the vehicle, is controlled in the normal case or in the uncritical operating case purely pneumatically by activating the brake pedal. The electric part of the electropneumatic brake device then consists in at least one additional vehicle movement dynamics controller which engages electrically only when critical situations such as e.g. locking of the brakes, skidding, yawing, oversteering, understeering occurs, using a braking intervention or steering braking intervention, e.g. in the form of ESP or ABS with traction control system valves on all the axles.
In a third variant of the electropneumatic service brake device, the brake pressure is open-loop or closed-loop controlled in some of the pneumatic wheel brake actuators of the vehicle and, if appropriate, of the trailer of the vehicle according to the first variant, and the brake pressure is open-loop or closed-loop controlled in some other of the pneumatic wheel brake actuators of the vehicle, and if appropriate, of the trailer of the vehicle.
In the event of the electropneumatic service brake device having an ESP function, a steering wheel angle sensor, a yaw rate sensor and a lateral acceleration sensor are already present and can be used to measure and monitor the effect of a steering braking intervention. The steering wheel angle sensor can furthermore also be used to sense the driver's steering request in order, if the driver himself is steering, to form a redundancy for a power steering system or the steering actuator of steer-by-wire steering device for steering braking operations. Therefore, in the case of a superimposition steering system with downstream hydraulic power steering system, the steering braking can be used in a supportive fashion if the hydraulic power steering system fails.
Alternatively or additionally, a sensor system is preferably provided for sensing the steering torque generated by the driver, for example a sensor for sensing the steering angle of the steered wheels for sensing the steering effect and/or a steering torque sensor in the steering column.
In order to ensure a high level of fail safety of the electric or electro-mechanical steering device with respect to its automatic actuation without involvement of a driver by the autopilot device or the driver assistance system, the electropneumatic service brake device is supplied with electrical energy by a first electric energy source or a first energy supply circuit which is independent of a second electric energy source or of a second energy supply circuit which supplies the electric or electro-mechanical steering device with electrical energy.
In this context, the steering requests of the autopilot device or of the driver assistance system which are generated in an automated fashion and without the involvement of the driver are input not only into the steering device but also into the electropneumatic brake device or “also read in” by the electropneumatic brake device.
If a fault then occurs in the second electric energy supply circuit or in the second electric energy source which supplies the steering device, or in the event of a fault in the steering device itself, this is detected by the electronic brake control device of the electropneumatic service brake device, e.g. through the absence of messages of the steering device, (e.g. on a databus to which both devices are connected), or by an explicit fault message of the steering device. It is also possible that the steering device is monitored by another control unit, and the fault is then communicated to the electropneumatic service brake device or the electronic brake control device thereof. In all these cases, the electropneumatic service brake device then implements the steering specifications or the steering request of the autopilot device or of the driver assistance system.
It is also possible that another control unit detects the failure of the steering device or its energy supply, calculates the brake pressures necessary for the steering braking and transmits them as wheel-specific or wheel-group-specific brake pressure specifications to the electropneumatic service brake device which then implements them. This other control unit can also be a part of the autopilot device.
Furthermore, it is to be ensured that the braking requests which are generated by the autopilot device continue to remain functionally capable even in the event of a fault in the electric energy supply or in the electric service brake circuit of the electropneumatic service brake device.
The invention proposes for this purpose that the pneumatic or electropneumatic service brake valve device which is always present in an electropneumatic service brake device or the foot-operated brake module which is present there in any case be modified in such a way that said device or module permits sensing of the brake pedal position and can modify the brake pressure output by at least one pneumatic channel of the service brake valve device, independently of activation of the brake pedal.
Such a pneumatic or electropneumatic service brake valve device which is then “active” or such an “active” foot-operated brake module as a synonym is disclosed in the abovementioned and until now unpublished German patent application having the file number DE 10 2014 112 014.0 of the applicant, wherein the disclosure thereof content in this respect is fully incorporated into the patent application which is present here.
The pneumatic part of this “active” foot-operated brake module functions as a service brake valve of a pneumatic service brake device and generates in response to activation of the brake pedal single-circuit or multi-circuit pneumatic brake pressures or brake control pressures in at least one pneumatic service brake circuit of the electropneumatic service brake device. At least if the electropneumatic service brake device is an electrically regulated or brake-pressure-regulated brake system (EBS), the active foot-operated brake module has a sensor system for sensing the driver's braking request in the form of an electric brake value generator. This sensor system is part of the electrical channel of the “active” foot-operated brake module or of the electric service brake circuit of the electropneumatic service brake device and, during fault-free operation, communicates the service braking request of the driver which is input via the service brake pedal.
So that the braking request of the driver is implemented even in the event of a fault in the electrical channel of the service brake valve device or in the electric service brake circuit of the electropneumatic service brake device, in the case of an electronically regulated brake system (EBS) the brake pressures or brake control pressures which are input into the at least one pneumatic service brake circuit are used as a backup.
The “active” foot-operated brake module also has the electrical channel and an electronic pressure open-loop control or closed-loop control device with which it can modify without the involvement of the driver, in particular increase or generate, brake pressures or brake control pressures in at least one pneumatic service brake circuit. It is therefore able to implement braking requests of a driver assistance system or of an autopilot device independently of the functioning of an electric brake pressure regulating process of the electropneumatic service brake device (EBS).
However, it is not necessary for the redundancy of the electric service brake circuit of the electropneumatic service brake device in the form of the “active” foot-operated brake module to open-loop or closed-loop control brake pressures in a wheel-specific or wheel-group-specific fashion. This is because the probability of a plurality of faults occurring simultaneously (to be precise a fault in the steering device and a fault in the service brake device) is very low. It is also not necessary for functions such as ABS, TCS or ESP which are required only in exceptional cases still to be able to be carried out in the event of a fault. Other functions which are not relevant to safety, such as e.g. lining wear control or the like, are not necessary in this situation either.
In order now to make the execution of the braking request generated by the autopilot device or by the driver assistance system more fail safe overall, the electric-pneumatic service brake device is supplied by the first electric energy supply circuit or the first electric energy source, while the “active” foot-operated brake module is supplied by the second electric energy supply circuit or the second electric energy source.
The braking request signals of the autopilot device are input, in particular, not only into the electropneumatic service brake device but also into the “active” foot-operated brake module or “also read in” by the “active” foot-operated brake module, e.g. on a databus to which both devices are connected.
If a failure or a fault then occurs in the first electric energy supply circuit or in the first electric energy source or else in the electric service brake circuit of the electropneumatic service brake device, this is detected by the active FBM, e.g. through the absence of the messages of the electropneumatic service brake device on the databus or through an explicit fault message of the electropneumatic service brake device. It is also possible for the electropneumatic service brake device to be monitored by another control unit and for it then to transmit a fault message to the “active” foot-operated brake module. This other control unit can also be part of the autopilot device or of the driver assistance system.
The “active” foot-operated brake module can then implement the braking specifications of the autopilot device or of the driver assistance system instead of the electropneumatic service brake device.
Because such a foot-operated brake module or such a service brake valve device can output a variable pressure between a minimum pressure and a maximum pressure which corresponds to the supply pressure in the compressed air supply it is also ensured that the braking effect in the event of a fault does not turn out to be lower than in the normal case. This is because in the normal case only a brake pressure which corresponds at maximum to the supply pressure can also be requested.
The electric equipment therefore preferably comprises an autopilot device or a driver assistance system which device or system inputs steering and/or braking request signals into the steering device and/or into the service brake device without involvement of the driver, wherein the steering and/or braking request signals are generated, in particular, as a function of driving operation conditions. Such driving operation conditions are to be understood as all conceivable conditions and circumstances which occur during a driving operation of a vehicle such as, for example, yawing behavior, rolling behavior and/or pitching behavior, braking behavior or acceleration behavior, as well as the distance and/or the relative speed with respect to a vehicle traveling ahead or else behavior in the stationary or parked state.
In this context, the steering and/or braking request signals of the autopilot device or of the driver assistance system, which are generated without the involvement of the driver, are preferably input into the steering device and into the electropneumatic service brake device and/or into the electropneumatic service brake valve device.
This is preferably carried out by connecting control units of the autopilot device, of the driver assistance system, of the steering device, of the electropneumatic service brake device and/or of the electropneumatic service brake valve device to a common databus.
In particular, according to a first embodiment, the electronic brake control device of the electropneumatic service brake device or electronics which differ therefrom is/are embodied in such a way that it/they detect(s) a failure or fault in the second electric energy supply circuit, in the second electric energy source or in the steering device, wherein the electronic brake control device or the electronics then actuate the electropneumatic service brake device in such a way that the latter implements the steering request signals, output by the autopilot device or the driver assistance system, in the form of wheel-specific or side-specific braking interventions, at the wheel brake actuators.
This first embodiment has, however, the disadvantage that the electropneumatic service brake device no longer receives any information about the steering and braking request signals of the driver both in the event of failure of the first electric supply circuit or of the first electric energy source as well as of the second electric supply circuit or of the second electric energy source, and therefore can implement said steering and braking request signals only via their at least one pneumatic service brake circuit. If a steering braking intervention requires the electropneumatic service brake device to switch off, for design reasons, the at least one pneumatic service brake circuit, said service brake device could no longer comply with the service braking request of the driver.
In order to compensate for this disadvantage, according to a second embodiment there is provision that at least one electric signal generator is provided, which is supplied with electrical energy by the first electric energy source or by the first energy supply circuit, can be activated by the service brake activation element. When the service brake activation element is activated, it inputs an electrical activation signal into the electronic brake control device or electronics which differ therefrom. In this context, the electric signal generator can be integrated into the electropneumatic service brake valve device and can be formed, in particular, by an electric switch.
According to a third embodiment, at least one electric signal generator is provided. The at least one electric signal generator is supplied with electrical energy by the first electric energy source or by the first energy supply circuit, and can be activated by the pneumatic brake pressure or brake control pressure in the at least one pneumatic service brake control circuit. When the service brake activation element is activated, it inputs an electrical activation signal into the electronic brake control device or electronics which differ therefrom. In this context, the electric signal generator can be integrated into the electropneumatic service brake valve device and can be formed, in particular, by an electric pressure sensor.
In the second and third embodiments, the electronic brake control device or the electronics is/are embodied, in particular, in such a way that it/they detect(s) a failure or fault in the second electric energy supply circuit in the second electric energy source or in the steering device, and the steering request signals which are output by the autopilot device or the driver assistance system are ignored and not implemented when such a fault is detected and when the activation signal is present.
According to one development, the steering device has an, in particular, hydraulic power steering system.
Therefore, a sensor system is provided. The sensor system is preferably additional with respect to the electric brake value generator and is supplied with electrical energy by the same first electric supply circuit as the electropneumatic service brake device, and detects that the driver wishes to brake. In this case, even when a fault is detected in the steering device no steering brake intervention is carried out since the driver is clearly in position and can assume control. The braking then takes place only with the at least one pneumatic service brake circuit of the electropneumatic brake service device. However, the second embodiment is not suitable for representing a redundancy of a power steering system of the steering device.
According to a fourth embodiment, the electropneumatic service brake valve device is additionally supplied with electrical energy by the first electric energy source or by the first energy supply circuit.
In the third and fourth embodiments, the electric service brake circuit of the electropneumatic service brake device receives the driver braking request even in the event of the failure of the first electric supply circuit or of the first electric energy source, and can implement said request. As a result, the brake pressures in the wheel brake actuators can be correspondingly modified for steering braking, and therefore both the driver braking request and the steering request can be implemented simultaneously. These embodiments are therefore also suitable for representing a redundancy of a power steering system of the steering device.
According to a further embodiment, the electronic evaluation device of the service brake valve device or electronics which differ therefrom is/are embodied in such a way that it/they detect(s) a failure or a fault in the first electric energy supply circuit, in the first electrical energy source or in the electric service brake circuit of the electropneumatic service brake device. The electronic evaluation device or the electronics then actuates/actuate the service brake valve device in such a way that the latter implements the braking request signals output by the autopilot device or by the driver assistance system in the form of braking interventions at the wheel brake actuators.
As stated above, in the invention the at least one control piston of the service brake valve device may be loaded not only by the first activation force when a braking request which is independent of the driver's request is present, but also by a second activation force which acts on the at least one control piston which is generated independently of a driver's braking request on the basis of electrical signals which are output by the electronic control device of the service brake valve device. The second activation force may be applied in parallel with the first activation force, and in the same direction as or in the opposite direction to the first activation force.
In other words, the first activation force which is dependent on a driver's braking request and/or the second activation force when a braking request is present which is independent of the driver's request, act in a parallel fashion on the control piston of the service brake valve device (the second activation force is generated on the basis of electrical signals which are output by the electronic control device of the service brake valve device). Consequently, either both activation forces (first and second activation forces) are together capable of activating the control piston and therefore also the double seat valve of the service brake valve, or else each activation force is individually capable of activating the control piston and therefore also the double seat valve of the service brake valve without the presence of the respective other activation force. In this context, the two activation forces can act on the control piston in the same direction or in opposite directions.
The first activation force which is generated as a function of a driver's braking request always acts on the at least one control piston in the same direction, specifically conditioned by the activation direction of the braking activation element in the direction of opening of the outlet seat of the double seat valve for aerating the at least one service brake circuit. Thus, the terms “in the same direction” or “in the opposite direction” are defined with respect to the direction of action of the first activation force. In the event of a first activation force not being present owing to a lack of a driver's braking request, the direction of action of said activation force on the at least one control piston is merely virtual, in order to be able to specify a reference for the direction of action of the second activation force which is then parallel with respect thereto.
Therefore, new control possibilities of the electropneumatic service brake device arise in that now the at least one pneumatic service brake circuit can, in addition to activation by the driver, now also be activated in an automated fashion electrically or electronically and therefore without the involvement of the driver when a braking request is present. The control or regulation of the at least one pneumatic service brake circuit of the electropneumatic service brake device by the electronic control device of the service brake valve device can then be carried out by any electrical control signals of any vehicle system or of any “authorized element” which can generate a braking request.
The advantages which can be achieved thereby are basically the fact that, within the actual pneumatic channel of an electropneumatic service brake valve device or of a foot-operated brake module, brake pressures or brake control pressures can be generated automatically for pneumatic service brake circuits independently of a driver's braking request. Therefore, corresponding brake pressures can then be generated, in particular, already in the service brake valve device, i.e. at a central location and for all the pneumatic service brake circuits which are connected to the service brake valve device, without the involvement or influence of the driver, in particular when a fault or a failure of the electric brake circuit of the electropneumatic service brake device has been detected, (in particular in the electrical energy supply thereof), in the electronic brake control device, or in the electropneumatic modulators. As a result, in the event of a fault or failure of the electric service brake circuit a further electric service brake circuit is also available and is then controlled by the electronic control device of the service brake valve device.
This meets the precondition that slight changes in an electropneumatic service brake valve device according to the prior art extend its functionality advantageously in the sense of an automatic brake control process which is brought about without the involvement of the driver, in that the electronic control device of said control process has open-loop or closed-loop control algorithms added to it by which the second activation force can then be generated using a preferably additionally provided electric, electro-hydraulic or electropneumatic actuator which is actuated by the electronic control device of the foot-operated brake module.
A service brake device which is provided with such a service brake valve device reacts in the case of automatic (extraneous) activation as well as in the case of a driver's braking request, for example with respect to the braking force distribution or the control of the trailer brakes. The service brake valve device is then suitable, in particular, for (partially) autonomous driving of the vehicle, as described above, within a vehicle column, since when a fault occurs in the electric service brake circuit, a braking operation which is controlled in an automated fashion is still possible via the at least one pneumatic service brake circuit.
Furthermore, the invention satisfies the fault tolerance which is requested for vehicle brakes by legislators. Furthermore, since the invention provides an additional at least partial electric service brake circuit whose electric component extends as far as the actuator which generates the second activation force, brake circuits with different designs are available with respect to the at least one pneumatic service brake circuit which then reduces the risk of both brake circuits being put out of operation by an identical or similar fault. Consequently, with the additional (partially) electric service brake circuit it is possible to output the maximum available braking power, since the at least one pneumatic service brake circuit can make use of the full supply pressure from a compressed air supply. Last but not least, existing electropneumatic service brake devices can easily be equipped by exchanging the service brake valve device with the invention, without the need to make a change to the electric cabling or pneumatic piping on the vehicle.
It is also essential for the invention that the driver can at any time override the braking request brought about by the second activation force by activating the braking activation element of the service brake valve device, because then the first activation force which is based on the driver's braking request is applied to the at least one control piston in parallel with the second activation force, which first actuation force is, under certain circumstances, larger than the second activation force and also directed in the opposite direction thereto.
This is because in many cases it may be desirable or necessary for the driver's braking request which is represented by the first activation force acting on the control piston to be overridden by generating a second activation force which is of corresponding magnitude and acts in the opposite direction, for example when in the case of column driving described above the driver would suddenly like to initiate a full braking operation at a short distance in each case from the vehicle driving ahead and the vehicle traveling behind, which would result in the risk of a rear-end accident.
Such a second activation force is particularly preferably also generated when a fault or a failure of the electric service brake circuit of the electropneumatic service brake device has been detected and when a braking request is present. In particular, the electronic brake control device, at least one electropneumatic axle modulator or else the electrical channel of the electropneumatic service brake valve can be effected by such a fault or a failure. However, a failure of the electric energy supply of the electric service brake circuit is also conceivable.
Of course, when there are a plurality of pneumatic channels of the service brake valve device, more than just a single control piston can be loaded by the second activation force or just a single control piston can be loaded, which then transmits the second activation force to a further activation piston.
The second activation force is preferably generated by at least one electric, electro-hydraulic or electropneumatic actuator. In this context, embodiments are then conceivable in which the second activation force is generated using an electropneumatic, electro-hydraulic or electro-mechanical actuator, such as e.g. solenoid valve, electric motor etc., which then acts directly or indirectly on the at least one control piston of the service brake valve device.
According to one development, the actuator for generating the second activation force includes at least one electropneumatic solenoid valve device which outputs at least one pneumatic control pressure as a function of the electrical signals for forming the second activation force. In response to a signal of the electronic control device of the service brake valve device, a control pressure is then output which acts directly or indirectly on the at least one control piston. This control pressure then generates the second activation force at the at least one control piston. Therefore, the second activation force is particularly preferably generated electropneumatically with the best possible use of the already present conditions at the service brake valve device.
In particular, in this context the control pressure which is output by the at least one solenoid valve device is measured by a sensor system and is regulated by comparison with a setpoint value in the electronic control device. The sensor system, the solenoid valve device together with the electronic control device form a control pressure regulator for regulating the pneumatic control pressure.
Therefore, there is preferably quite generally provision that at least one of the second activation force which acts on the at least one control piston, the activation travel, of the at least one control piston of the service brake valve device from the application of the second activation force and a variable which generates the second activation force (e.g. the abovementioned pneumatic control pressure), are measured as actual variables and compared with a setpoint variable as part of a closed-loop control. By using the here optional closed-loop control of the second activation force or of one of the above variables related thereto it is possible to increase the accuracy of the brake pressure setting.
In order to implement such a closed-loop control function it is possible to provide sensors which measure the variables (e.g. the second activation force which acts on the at least one control piston, the activation travel, of the at least one control piston from application of the second activation force, and a variable which generates the second activation force) as actual variables, and provide a closed-loop controller by which the actual variable is compared with a setpoint variable as part of a closed-loop control process.
In particular, the pneumatic control pressure can be input into at least one control chamber of the electropneumatic service brake valve device, which control chamber is bounded by the at least one control piston, such that in the case of aeration the pneumatic control pressure brings about a second activation force (in the same direction as or the opposite direction to the first activation force) on the at least one control piston.
In order to implement such a functionality in the simplest way possible, a first control chamber can also be arranged with respect to the at least one control piston in such a way that, by aeration of the first control chamber, a second activation force in the same direction as the first activation force is generated on the at least one control piston. However, in addition, a second control chamber is arranged in such a way that, by aeration of the second control chamber, a second activation force which is in the opposite direction to the first activation force is generated on the at least one control piston.
In this context there can preferably be provision that the first control chamber can be aerated or vented by a first solenoid valve device or by a first control pressure regulator and the second control chamber can be aerated or vented independently thereof by a second solenoid valve device or by a second control pressure regulator.
Last but not least, the at least one control piston can be a double piston with two pistons which are connected by a piston rod, a first of which bounds the first control chamber, and a second of which bounds the second control chamber, wherein the first control chamber and the second control chamber are adjacent to faces of an inner wall of the service brake valve device which point away from one another and through which the piston rod projects in a seal-forming fashion.
The invention also relates to a vehicle having such an at least partially electric braking and steering device.
Advantageous developments of the invention can be found in the patent claims, the description and the drawings. The advantages of features and of combinations of a plurality of features which are specified in the introduction to the description are merely exemplary and can come into effect alternatively or cumulatively without the advantages necessarily having to be achieved by embodiments according to the invention. Further features can be found in the drawings, in particular the illustrated geometries and the relative dimensions of a plurality of components with respect to one another and their relative arrangement and operative connection. The combination of features of different embodiments of the invention or of features of different patent claims is also possible in ways which depart from the selected back-references of the patent claims and said combination is hereby suggested. This also relates to such features which are illustrated in separate drawings or are mentioned in the description thereof. These features can also be combined with features of different patent claims. Likewise, features, specified in the patent claims, for other embodiments of the invention can be eliminated. Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.